Ok, just back from the Tesco where I bought it. Explained the problem and without any pause he said "That's not right, got your receipt? I'll give you a new one now".
I said he'd better check it over himself first, which he then did.
Used my charger and Tab, nothing after 3/4 mins, no battery symbol.
Used their charger on my Tab, nothing, no battery symbol after 3/4 mins.
Used my charger on their Tab, nothing after 3/4, then the battery symbol came up and the Tab crashed. He tried a couple of times to get their Tab to boot up with my charger in, and it wouldn't.
I suggested he unplug it before it buggers up their Tab as well.
Anyway, short story long, back in 2 weeks with receipt for a complete replacement.
Then the pain of downloading 114 Apps and database stuff down onto it again ARGHHHHH.
Would like to try a new charger on it to see if the Tab is still OK though, leave it to charge for an hour or two with a new charger.